Tension measuring apparatus having a heat flow sensor that detects a heat flow caused by an elastic deformation of an elastic body

ABSTRACT

A tension measuring apparatus includes a displacement part that is displaced in accordance with tension or a change of the tension of a wire rod to be measured when the displacement part is caused to abut against the wire rod to receive the tension of the wire rod, an elastic body that is elastically deformed in accordance with displacement of the displacement part, and a heat flow sensor that detects a heat flow caused by elastic deformation of the elastic body.

This application claims priority to Japanese Patent Application No. 2016-81188 filed on Apr. 14, 2016, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tension measuring apparatus for measuring the tension of a wire rod.

2. Description of Related Art

There is a demand for a technique for controlling the tension of a wire rod. For example, an automatic winding machine for winding a wire rod on a bobbin is required to maintain the tension of the wire rod constant for the purpose of increasing the quality and working efficiency.

Japanese Patent Application Laid-open No. 64S-41207 discloses a technique in which a tension control apparatus is used for controlling the tension applied to a wire rod by this apparatus so that the tension is maintained constant. More specifically, the tension control apparatus described in this patent document includes an arm for supporting a wire, a tension roller for applying a tension to the wire rod, a rotational resistance imparting mechanism for imparting a rotational resistance to the tension roller and a controller for issuing commands to the rotational resistance imparting mechanism. According to the technique disclosed in this patent document, the tension of a wire rod is generated by supporting the wire rod with the arm. Further, the tension of the wire rod can be changed at any time by changing the rotational resistance which the rotational resistance imparting mechanism applies to the tension roller based on the command received from the controller. The command issued from the controller is set taking into account the aging variation of the tension of the wire rod while the automatic winding machine is in operation.

That is, according to the technique disclosed in this patent document, the tension of a wire rod is controlled by supporting the wire rod with the arm, and adjusting the rotational resistance imparted to the tension roller by the rotational resistance imparting mechanism.

As explained above, the tension control apparatus described in the above patent document is configured to adjust the tension of a wire rod by controlling each of the support resistance of the arm and the rotational resistance of the tension roller. This conventional tension control apparatus has a problem that there may occur a control error due to deflection or vibration of the arm, or an error in controlling the tension roller by the rotational resistance imparting mechanism. Accordingly, this conventional tension control apparatus is not capable of controlling the tension of a wire rod with a sufficiently high degree of accuracy. Under the circumstances, there is a strong demand for a technique that enables accurately measuring tension of a wire rod.

It is known to use a load cell that converts a load into an electric signal for measuring the tension of a wire as the load. Such a load cell is installed such that its sensing part including a sensor is in direct contact with a wire rod so that the sensing part directly receives the tension of the wire rod. Accordingly, there is a concern that the sensor may be damaged by the tension of the wire rod.

SUMMARY

An exemplary embodiment provides a tension measuring apparatus including:

a displacement part that is displaced in accordance with tension or a change of the tension of a wire rod when the displacement part is caused to abut against the wire rod to receive the tension of the wire rod;

an elastic body that is elastically deformed in accordance with displacement of the displacement part; and

a heat flow sensor that detects a heat flow caused by elastic deformation of the elastic body.

According to the exemplary embodiment, there is provided a tension measuring apparatus capable of directly measuring the tension of a wire rod, and whose sensor is not easily damaged.

Other advantages and features of the invention will become apparent from the following description including the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a diagram showing the overall structure of a tension measuring apparatus according to a first embodiment of the invention;

FIG. 2 is another diagram showing the overall structure of the tension measuring apparatus according to the first embodiment of the invention;

FIG. 3 is a plan view of a heat flow sensor included in the tension measuring apparatus according to the first embodiment of the invention;

FIG. 4 is a cross-sectional view of FIG. 3 taken along line IV-IV;

FIG. 5 is a diagram showing the overall structure of a tension measuring apparatus according to a second embodiment of the invention;

FIG. 6 is another diagram showing the overall structure of the tension measuring apparatus according to the second embodiment of the invention;

FIG. 7 is a diagram showing the overall structure of a tension measuring apparatus according to a third embodiment of the invention;

FIG. 8 is another diagram showing the overall structure of the tension measuring apparatus according to the third embodiment of the invention;

FIG. 9 is a diagram showing the overall structure of a tension measuring apparatus according to a fourth embodiment of the invention;

FIG. 10 is another diagram showing the overall structure of the tension measuring apparatus according to the fourth embodiment of the invention;

FIG. 11 is a diagram showing the overall structure of a tension measuring apparatus according to a variant embodiment of the invention; and

FIG. 12 is another diagram showing the overall structure of the tension measuring apparatus according to the variant embodiment of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

First Embodiment

A tension measuring apparatus 1 according to a first embodiment of the invention is described with reference to FIGS. 1 to 4. The tension measuring apparatus 1 is used for measuring the tension of a wire rod 100 which is fed to a bobbin to be wound thereon by an automatic winding machine. FIG. 1 shows the overall structure of the tension measuring apparatus 1 at a point of time of starting a measurement. FIG. 2 is shows the overall structure of the tension measuring apparatus 1 at a point of time when the tension of the wire rod 100 has increased after starting the measurement. The arrow Y1 in FIG. 1 shows the direction of deformation of an elastic body 3 when the tension of the wire rod 100 has increased.

As shown in FIGS. 1 and 2, the tension measuring apparatus 1 includes a displacement part 2, the elastic body 3, a heat flow sensor 4, plate-like members 5 and 6, a tension calculation part 7 and a display part 8. The plate-like member 6, the heat flow sensor 4, the elastic body 3, the plate-like member 5 and the displacement part 2 are stacked in this order from the downward side as shown in FIGS. 1 and 2.

The displacement part 2 includes a portion which the wire rod 100 abuts against to receive the tension of the wire rod 100. The displacement part 2 is displaced in accordance with the tension of the wire rod 100 against which the portion of the displacement part 2 is caused to abut. As shown in FIGS. 1 and 2, the displacement part 2 includes a proximal portion 2 a and a roller portion 2 b.

The proximal portion 2 a of the displacement part 2 directly or indirectly connects with the elastic part 3 to apply a pressing force to the elastic part 3 depending on the tension of the wire rod 100. In this embodiment, as shown in FIGS. 1 and 2, the proximal portion 2 a of the displacement part 2 is formed in a roughly cubic shape, and connects to the elastic body 3 through the plate-like member 5. The proximal portion 2 a of the displacement part 2 is made of stainless steel, for example. The plate-like member 5 is made of stainless steel, for example.

The roller portion 2 b is a cylindrical rotating body rotatably supported by the proximal portion 2 a. The roller portion 2 b rotates when it is caused to abut against the wire rod 100, to feed the wire rod 100 in the feed direction shown by the arrow in FIGS. 1 and 2. The roller portion 2 b is made of Delrin resin, for example.

The proximal portion 2 a and the roller portion 2 b are displaced in accordance with the tension of the wire rod 100. Specifically, the proximal portion 2 a is displaced together with the roller portion 2 b in the direction perpendicular to the feed direction when the roller portion 2 b receives the tension of the wire rod 100. As a result of the displacement of the proximal portion 2 a, the elastic body 3 is pressed by the plate-like member 5 and is deformed accordingly.

The elastic body 3 is deformed in accordance with the displacement of the displacement part 2 caused by the tension or a change of the tension of the wire rod 100. The elastic body 3 is made of urethane rubber, for example. The elastic modulus of the material of the elastic body 3 is smaller than that of the displacement part 2 in this embodiment. However, the elastic modulus of the material of the elastic body 3 may be larger than that of the displacement part 2.

The heat flow sensor 4 is a sensor for detecting a heat flow caused by an elastic deformation of the elastic body 3. The heat flow sensor 4 is disposed at a position where a heat flow caused by an elastic deformation of the elastic body 3 can be detected. In this embodiment, the heat flow sensor 4 is disposed so as to be in contact with the elastic body 3. The heat flow sensor 4 outputs a sensor signal depending on a heat flow directing from the inside to the outside of the elastic body 3.

As shown in FIGS. 3 and 4, the heat flow sensor 4 has a structure in which an insulating substrate 40, a front surface protecting member 41 and a back surface protecting member 42 are integrated such that first inter-layer connecting members 43 and second inter-layer connecting members 44 are connected in series alternately therein. In FIG. 3, the front surface protecting member 41 is omitted from illustration. Each of the insulating substrate 40, the front surface protecting member 41 and the back surface protecting member 42 is made of resin material having flexibility (thermoplastic resin, for example) formed in a film shape. The insulating substrate 40 is formed with first via holes 401 and second via holes 402 which penetrate through in the thickness direction. Each of the first via holes 401 is filled with a first inter-layer connecting member 43 made of thermoelectric material (metal or semiconductor, for example). Each of the second via holes 402 is filled with a second inter-layer connecting member 44 made of thermoelectric material (metal or semiconductor, for example), which is different from the first inter-layer connecting member 43. A front surface conductor pattern 411 is disposed on the front surface 40 a of the insulating substrate 40. The front surface conductor pattern 411 makes a connecting part that connects one end of the first inter-layer connecting member 43 to one end of the second inter-layer connecting member 44. A back surface conductor pattern 421 is disposed on the back surface 40 b of the insulating substrate 40. The back surface conductor pattern 421 makes a connecting part that connects the other end of the first inter-layer connecting member 43 to the other end of the second inter-layer connecting member 44. In the following, the side on the one end of the first or second inter-layer connecting member 43 or 44, that is, the side on the front surface protecting member 41 is referred to as the front side of the heat flow sensor 4. Likewise, the side on the other end of the first or second inter-layer connecting member 43 or 44, that is, the side on the back surface protecting member 42 is referred to as the back side of the heat flow sensor 4.

As shown in FIGS. 1 and 2, the heat flow sensor 4 having the above described structure is disposed such that the elastic body 3 is located on the front side of the heat flow sensor 4. The heat flow sensor 4 is fixed to the plate-like member 6 which is disposed on the back side of the heat flow sensor 4.

When a heat flow passes the heat flow sensor 4 in the thickness direction of the heat flow sensor 4, a difference in temperature occurs between the front side and the back side of the heat flow sensor 4. More specifically, when a heat flow passes the heat flow sensor 4 in the thickness direction of the heat flow sensor 4, a difference in temperature occurs between the connecting parts on the side of the one ends of the first and second inter-layer connecting members 43 and 44 and the connecting parts on the side of the other ends of the first and second inter-layer connecting members 43 and 44. As a result, an electromotive force occurs in the first and second inter-layer connecting members 43 and 44 due to the Seebeck effect. The heat flow sensor 4 outputs, as a sensor signal (a voltage signal, for example) the electromotive force depending on the heat flow passing between the front side and the back side of the heat flow sensor 4. In this embodiment, the heat flow sensor 4 is configured to generate a positive electromotive force when a heat flow passes from the front side to the back side of the heat flow sensor 4.

The elastic body 3 generates heat therein when the elastic body 3 is compressed or expanded, and generates cold therein when the elastic body 3 returns from a state of being applied with an external force from outside to be compressed to the initial state after the external force is released. There is a correlation between the magnitude of the absolute value of an electromotive force generated by the heat flow sensor 4 and a deformation of the elastic body 3 (the amount or variation of a deformation of the elastic body 3, for example). Generally, as the deformation amount of the elastic body 3 increases, a heat flux caused by the deformation of the elastic body 3 increases and the temperature difference between the front side and the back side of the heat flow sensor 4 increases. Accordingly, as the deformation amount of the elastic body 3 increases, the temperature difference between the connecting parts on the side of the one ends of the first and second inter-layer connecting members 43 and 44 and the connecting parts on the side of the other ends of the first and second inter-layer connecting members 43 and 44 increases, as result of which the absolute value of the electromotive force generated by the heat flow sensor 4 increases.

Since the heat flow sensor 4 has the above described structure, it can be disposed on various surfaces which are not flat (curved surfaces, for example). In addition, since the thickness of the heat flow sensor 4 can be made small while ensuring a sufficiently large electromotive force to be generated, it is possible to reduce a detection error by reducing the thermal resistance in the heat flow sensor 4 by reducing the thickness of the heat flow sensor 4.

The tension calculation part 7 calculates the tension of change of the tension of the wire rod 100 based on a heat flow caused by an elastic deformation of the elastic body 3, which is detected by the heat flow sensor 4. More specifically, the tension calculation part 7 calculates the tension or a change of the tension of the wire rod 100 based on the sensor signal outputted from the heat flow sensor 4, that is, an electromotive force that has occurred in the heat flow sensor 4. The tension calculation part 7 is an electronic control unit comprised of a microcomputer, a memory as a storage device, and peripheral circuits. The memory stores data representing a relationship between the tension of the wire rod 100 and the electromotive force to be generated by the heat flow sensor 4 when the plate-like member 6 is placed at a predetermined position. Further, the memory stores data representing a relationship between a change of the tension of the wire rod 100 and the electromotive force to be generated by the heat flow sensor 4. The memory is a non-transitory storage medium.

Also, the tension calculation part 7 controls the operation of the display part 8 by performing a calculation process in accordance with programs stored in the memory, so that the tension or a change of the tension of the wire rod 100 is displayed on the display part 8.

Next, the operation of the tension measuring apparatus 1 having the above described structure is explained.

As shown in FIG. 1, the tension measuring apparatus 1 is placed at a predetermined position, and the rod wire 100 is caused to abut against the displacement part 2. At this time, the displacement part 2 displaces depending on the position of the displacement part 2 and the tension of the wire rod 100, causing the elastic body 3 to be compressed to a certain extent.

When the elastic body 3 is compressed as above, the molecules inside the elastic body 3 are aligned as a result of which heat is generated inside the elastic body 3. Accordingly, a heat flow from the inside of the elastic body 3 to the outside occurs. Since this heat flow passes the front side of the heat flow sensor 4, there occurs a temperature difference between the front side and the back side of the heat flow sensor 4. As a result, an electromotive force occurs as the sensor signal depending on the tension of the wire rod 100, and the tension calculation part 7 calculates the tension of the wire rod 100 based on the sensor signal. Specifically, to calculate the tension of the wire rod 100, the tension calculation part 7 reads the data representing the relationship between the tension of the wire rod 100 and the electromotive force generated by the heat flow sensor 4 from the memory. The tension of the wire rod 100 calculated by the tension calculation part 7 at this time is stored in the memory as an initial tension at the time of start of measurement. Incidentally, the heat flux caused by compressing the elastic body 3 at the time of start of measurement is released to the outside with the passage of time, and becomes undetectable after an elapse of a predetermined time.

In a case where the tension of the wire rod 100 increases after the start of measurement, the displacement part 2 is displaced downward in FIG. 2, and as a result the elastic body 3 is compressed more then than at the start of measurement. In this case, an electromotive force occurs depending on the degree of change of the tension of the wire rod 100. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has increased from the initial tension as a second stage tension. If the tension of the wire rod 100 increases beyond a predetermined value, the wire rod 100 becomes roughly linear in shape.

In a case where the tension of the wire rod 100 decreases after the start of measurement or after being compressed more after the start of measurement, the displacement part 2 is displaced upward in FIG. 2 to return to the initial state. In this case, the compression of the elastic body 3 is released and the elastic body 3 restores from the elastic deformation, as a result of which cold occurs inside the elastic body 3. As a result, since the temperature of the front side of the heat flow sensor 4 decreases, the temperature difference between the front side and the back side of the heat flow sensor 4 is changed from that before the decrease of the tension of the wire rod 100. Accordingly, there occurs a change in the electromotive force generated by the heat flow sensor 4. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has decreased from the initial tension or the second stage tension. The electromotive force generated by the heat flow sensor 4 at this moment is lower than that before the tension of the wire rod 100 decreases. When the sign of the temperature difference between the front side and the back side of the heat flow sensor 4 changes after the tension of the wire rod 100 decreases, also the sign of the electromotive force changes. The tension calculation part 7 causes the display part 8 to display change of the tension of the wire rod 100.

According to the tension measuring apparatus 1, the displacement part 2 is in accordance with the tension or a change of the tension of the wire rod 100, and the elastic body 3 is deformed in accordance with the displacement of the displacement part 2. The tension measuring apparatus 1 is capable of detecting a change of the heat flow due to deformation of the elastic body 3 by the heat flow sensor 4 to measure the tension and a change of the tension of the wire rod 100. The tension measuring apparatus 1 is configured such that the tension of the wire rod 100 is not directly received by the heat flow sensor 4, but the elastic body 3 is caused to abut against the heat flow sensor 4. Therefore, according to the tension measuring apparatus 1, it is possible to prevent the problem in the conventional art which uses a load cell that a sensor may be easily damaged.

Incidentally, according to the tension measuring apparatus 1, the tension or a change of the tension of the wire rod 100 can be measured even while the automatic winding machine is in operation to feed the wire rod 100. Further, according to the tension measuring apparatus 1, the tension or a change of the tension of the wire rod 100 can be measured even while the automatic winding machine is out of operation, and the wire rod 100 is stationary.

As described above, the tension measuring apparatus 1 includes the displacement part 2 which is displaced in accordance with the tension or a change of the tension of the wire rod 100 when it is caused to abut against the wire rod 100 to receive the tension of the wire rod 100, the elastic body 3 which is elastically deformed in accordance with the displacement of the displacement part 2, and the heat flow sensor 4 which detects a heat flow caused by the elastic deformation of the elastic body 3.

In the tension measuring apparatus 1, the displacement part 2 is displaced in accordance with the tension or a change of the tension of the wire rod 100, and the elastic body 3 is deformed in accordance with the deformation of the displacement part 2. According to the tension measuring apparatus 1, it is possible to detect a change of a heat flow caused by a deformation of the elastic body 3 to measure the tension or a change of the tension of the wire rod 100. As described above, the tension measuring apparatus 1 is configured such that the tension of the wire rod 100 is not directly received by the heat flow sensor 4, but the elastic body 3 is caused to abut against the heat flow sensor 4. Therefore, according to the tension measuring apparatus 1, it is possible to prevent the problem in the conventional art which uses a load cell that a sensor may be easily damaged.

In the tension measuring apparatus 1, the displacement part 2 includes the roller portion 2 b which rotates when caused to abut against the wire rod 100 to feed the wire rod 100.

Accordingly, the tension measuring apparatus 1 can displace the displacement part 2 to measure the tension of the wire rod 1200 while feeding the wire rod 100 smoothly using the roller portion 2 b.

Second Embodiment

Next a second embodiment of the invention is described with a focus on differences with the first embodiment referring to FIGS. 5 and 6.

In FIGS. 5 and 6, the tension calculation part 7 and the display part 8 are omitted from illustration. In FIG. 5, the arrow Y2 shows the direction of displacement of the displacement part 2 at a time when the tension of the wire rod 100 has changed, and the arrow Y3 shows the direction of displacement of the elastic body 3 at a time when the tension of the wire rod 100 has increased.

As shown in FIGS. 5 and 6, the tension measuring apparatus 1 according to the second embodiment includes, in addition to the displacement part 2, the elastic body 3, the heat flow sensor 4 and the display part 8, a case part 9 housing the elastic body 3, a support mechanism 10 for causing the case part 9 to support the displacement part 2, a radiator 11, and a plate-like member 12.

In this embodiment, the displacement part 2 rotates with the support mechanism 10 as a fulcrum in accordance with the tension or a change of the tension of the wire rod 100 at a time when the displacement part 2 is caused to abut against the wire rod 100. As shown in FIGS. 5 and 6, the displacement part 2 includes a proximal portion 2 c having a rod shape and a roller portion 2 d.

The roller portion 2 d is formed in a distal end of the proximal portion 2 c. The proximal portion 2 c is made of stainless steel, for example. The roller portion 2 d is made of Delrin resin, for example.

The roller portion 2 d is a cylindrical rotating body supported by the case part 9 so as to be rotatable independently of the whole rotation of the displacement part 2 to feed the wire rod 100. As shown in FIGS. 5 and 6, the roller portion 2 d rotates when it is caused to abut against the wire rod 100, and as a result it feeds the wire rod 100 abutting against the roller portion 2 d in the feed direction of the arrow in FIG. 6.

In this embodiment, the elastic body 3 is disposed on one surface of the plate-like member 12, which faces the displacement part 2. The elastic body 3 is disposed so as to be abutted against the proximal portion 2 c of the displacement part 2.

The heat flow sensor 4 is disposed on the other surface of the plate-like member 12, which does not face the displacement part 2.

The support mechanism 10 is a mechanism for enabling the case part 9 to rotatably support the displacement part 2. The support mechanism 10 includes a rotation shaft which makes an axis of rotation of the displacement part 2. This rotation shaft is inserted in a through hole formed in the proximal portion 2 c of the displacement part 2. In the tension measuring apparatus 1 of this embodiment, the distance between the support mechanism 10 and the roller portion 2 d is longer than the distance between the support mechanism 10 and a portion of the proximal portion 2 c at which the displacement part 2 is caused to abut against the elastic body 3. That is, in this embodiment, the support mechanism 10 makes a fulcrum, the portion of the proximal portion 2 c which abuts against the elastic body 3 makes a point of action, and the roller portion 2 d makes a point of effort, so that the elastic body 3 is deformed using the principle of leverage.

The radiator 11 is comprised of a heat dissipation fin having a large heat dissipation area for dissipating the heat of the inside of the heat flow sensor 4 and its vicinity to the outside. As shown in FIGS. 5 and 6, the radiator 11 is disposed on the side opposite the elastic body 3 with the heat sensor 4 between them.

The plate-like member 12 is supported by the case part 9, and supports the elastic body 3 at one surface thereof. The heat flow sensor 4 and the radiator 11 are fixed to the other surface of the plate-like member 12. The plate-like member 12 is made of stainless steel, for example. The plate-like member 12 functions as an intervening part for preventing a force caused by an elastic deformation of the elastic body 3 in accordance with the tension of the wire rod 100 from affecting the heat flow sensor 4. In this embodiment, since the plate-like member 12 is provided as an intervening part, the heat flow sensor 4 can be prevented from being damaged.

In the tension measuring apparatus 1 according to the second embodiment, the displacement part 2 is deformed in accordance with the tension or a change of the tension of the wire rod 100 as in the case of the first embodiment. Therefore, also according to the second embodiment, since the elastic body 3 is deformed in accordance with displacement of the displacement part 2, the tension or a change of the tension of the wire rod 100 can be measured by detecting a change of a heat flow caused by the deformation of the elastic body.

Next, the operation of the tension measuring apparatus 1 according to the second embodiment is explained.

As shown in FIG. 5, the tension measuring apparatus 1 is placed at a predetermined position, and the rod wire 100 is caused to abut against the displacement part 2. At this time, the displacement part 2 rotates with the support mechanism 10 as a fulcrum in accordance with the position of the displacement part 2 and the tension or a change of the tension of the wire rod 100, causing the elastic body 3 to be compressed to some extent.

When the elastic body 3 is compressed as above, the molecules inside the elastic body 3 are aligned, as a result of which heat is generated inside the elastic body 3. Accordingly, a heat flow from the inside of the elastic body 3 to the outside occurs. Since this heat flow passes the front side of the heat flow sensor 4, there occurs a temperature difference between the front side and the back side of the heat flow sensor 4. As a result, an electromotive force occurs as the sensor signal corresponding to the tension of the wire rod 100, and the tension calculation part 7 calculates the tension of the wire rod 100 based on the sensor signal.

In a case where the tension of the wire rod 100 increases after the start of measurement, the displacement part 2 rotates downward with the support mechanism 10 as a fulcrum downward in FIG. 6, and as a result, the elastic body 3 is compressed more then than at the start of measurement. In this case, an electromotive force in accordance with the degree of a change of the tension of the wire rod 100 occurs. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has increased. If the tension of the wire rod 100 increases beyond a predetermined value, the wire rod 100 becomes roughly linear in shape.

In a case where the tension of the wire rod 100 decreases after the start of measurement or after being compressed more after the start of measurement, the displacement part 2 rotates upward in FIG. 6 with the support mechanism 10 as a fulcrum. In this case, the compression of the elastic body 3 is released and the elastic body 3 restores from the elastic deformation, as a result of which cold occurs inside the elastic body 3. As a result, since the temperature of the front side of the heat flow sensor 4 decreases, the temperature difference between the front side and the back side of the heat flow sensor 4 is changed from that before the decrease of the tension of the wire rod 100. Accordingly, there occurs a change in the electromotive force generated by the feat flow sensor 4. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has decreased. The electromotive force generated by the heat flow sensor 4 at this moment is lower than that before the tension of the wire rod 4 decreases. When the sign of the temperature difference between the front side and the back side of the heat flow sensor 4 changes after the tension of the wire rod 100 decreases, also the sign of the electromotive force changes.

As described above, according to the tension measuring apparatus 1 of this embodiment, both the tension and a change of the tension can be measured like the first embodiment.

In addition, in the tension measuring apparatus 1 of this embodiment, the tension of the wire rod 100 is not directly received by the heat flow sensor 4, but the elastic body 3 is abutted against the heat flow sensor 4 and the plate-like member 12 is intervened between the displacement part 2 and the heat flow sensor 4. Accordingly, the heat flow sensor 4 is not easily damaged.

Further, in the tension measuring apparatus 1 of this embodiment, the displacement part 2 is caused to rotate by the tension of the wire rod 100, and the elastic body 3 is deformed by the rotation of the displacement part 2. That is, in the tension measuring apparatus 1 of this embodiment, the tension of the wire rod 100 is converted to a large force using the principle of leverage. Therefore, since the position of the point of effort (that is, the part of the proximal portion of the displacement part 2 which is caused to abut against the elastic body 3) to the fulcrum (that is, the support mechanism 10) and the point of effort (that is, the roller portion 2 d) can be adjusted, the relationship between the tension of the wire rod 100 and the displacement of the elastic body 3 or the relationship between the tension of the wire rod 100 and the electromotive force of the heat flow sensor 4 can be set in a wide range. For example, it is possible to accommodate such a case where the elastic body 3 should be deformed greatly even when the tension of the wire rod 100 is small by increasing the distance between the fulcrum (that is, the supporting mechanism 10) of the displacement part 2 and the point of effort (that is, the roller portion 2 d).

Third Embodiment

Next a third embodiment of the invention is described with a focus on differences with the first embodiment referring to FIGS. 7 and 8.

In FIGS. 7 and 8, the tension calculation part 7 and the display part 8 are omitted from illustration. In FIG. 7, the arrow Y4 shows the direction of displacement of the displacement part 2 at a time when the tension of the wire rod 100 has changed, and the arrows Y5 to Y8 show the directions of displacement of the elastic body 3 at a time when the tension of the wire rod 100 has increased.

In this embodiment, the displacement part 2 includes the proximal portion 2 c and a roller portion 2 d. As shown in FIGS. 7 and 8, the proximal portion 2 c of the displacement part 2 includes a rod-shaped portion 2 ca formed with the roller portion 2 d at its one distal end and formed with a polyhedral portion 2 cb at its other distal end. In this embodiment, the polyhedral portion 2 cb of the displacement part 2 has a cubic shape. The rod-shaped portion 2 ca and the polyhedral portion 2 cb of the displacement part 2 rotate together with the support mechanism 10 as a fulcrum. The rod-shaped portion 2 ca of the displacement part 2 is made of stainless steel, for example. The roller portion 2 d is made of Delrin resin, for example. The polyhedral portion 2 cb of the displacement part 2 is made of stainless steel, for example.

As shown in FIGS. 7 and 8, the elastic body 3 is disposed at a plurality of positions around the polyhedral portion 2 cb in this embodiment. Each of the plurality of the elastic bodies 3 faces an opposite one of a plurality of the surfaces of the polyhedral portion 2 cb. That is, the elastic bodies 3 are disposed such that each one of them abuts a corresponding one of the surfaces of the polyhedral portion 2 cb and is deformed when the polyhedral portion 2 cb rotates. In this embodiment, the elastic bodies 3 are four spherical elastic bodies. When the polyhedral portion 2 cb of the displacement part 2 rotates with the support mechanism 10 as a fulcrum, the four spherical elastic bodies are compressed by the displacement of the surfaces of the polyhedral portion 2 cb due to the rotation.

In the third embodiment, the plate-like member 12 is removed. The case part 9 functions as the intervening part that prevents a force caused by an elastic deformation of the elastic body due to the tension of the wire rod 100 from affecting the heat flow sensor 4.

Next, the operation of the tension measuring apparatus 1 according to the third embodiment is explained.

As shown in FIGS. 7 and 8, the tension measuring apparatus 1 is placed at a predetermined position, and the wire rod 100 is caused to abut against the displacement part 2. At this time, the displacement part 2 is in a state of being caused to abut against the elastic body 3 so as to slightly compress the elastic body 3.

In this state, since the elastic body 3 is only slightly compressed, the electromotive force generated in the heat flow sensor 4 at this moment (that is, at the start of measurement) is approximately zero.

In a case where the tension of the wire rod 100 increases thereafter, the displacement part 2 rotates in the direction A or B with the support mechanism 10 as a fulcrum. Here, it is assumed that the displacement part 2 rotates in the direction A. The elastic body 3 is compressed more then than at the start of measurement. In this case, there occurs an electromotive force in accordance with the degree of a change of the tension of the wire rod. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has increased. If the tension of the wire rod 100 increases beyond a predetermined value, the wire rod 100 becomes roughly linear in shape.

In a case where the tension of the wire rod 100 decreases after the start of measurement or after being compressed more after the start of measurement, the displacement part 2 rotates in the direction B in FIG. 7 with the support mechanism 10 as a fulcrum. In this case, the compression of the elastic body 3 is released and the elastic body 3 restores from the elastic deformation, as a result of which cold occurs inside the elastic body 3. As a result, since the temperature of the front side of the heat flow sensor 4 decreases, the temperature difference between the front side and the back side of the heat flow sensor 4 is changed from that before the decrease of the tension of the wire rod 100. Accordingly, there occurs a change in the electromotive force generated by the feat flow sensor 4. The tension calculation part 7 calculates the tension of the wire rod 100 at this moment that has decreased. The electromotive force generated by the heat flow sensor 4 at this moment is lower than that before the tension of the wire rod 4 decreases. When the sign of the temperature difference between the front side and the back side of the heat flow sensor 4 changes after the tension of the wire rod 100 decreases, also the sign of the electromotive force changes.

As described above, according to the tension measuring apparatus 1 of this embodiment, both the tension and a change of the tension of the wire rod 100 can be measured like the first embodiment.

In this embodiment, the heat flow sensor 4 can be prevented from being damaged, like in the fourth embodiment.

Therefore, the relationship between the tension of the wire rod 100 and the displacement of the elastic body 3 or the relationship between the tension of the wire rod 100 and the electromotive force of the heat flow sensor 4 can be set in a wide range.

Further, since the elastic bodies 3 can be deformed efficiently using the respective surfaces of the polyhedral portion 2 cb, it is possible to increase the electromotive force of the heat flow rate sensor 4 efficiently.

Fourth Embodiment

Next a fourth embodiment of the invention is described with a focus on differences with the first embodiment referring to FIGS. 9 and 10.

In FIGS. 9 and 10, the tension calculation part 7 and the display part 8 are omitted from illustration. In FIG. 9, the arrow Y9 shows the direction of displacement of the displacement part 2 at a time when the tension of the wire rod 100 has changed, the arrow Y10 shows the direction of displacement of the elastic body 3 at a time when the tension of the wire rod 100 has increased causing the displacement part 2 to displace in the direction shown by the arrow D, and the arrow Y11 shows the direction of displacement of the elastic body 3 at a time when the tension of the wire rod 100 has increased causing the displacement part 2 to displace in the direction shown by the arrow C.

As shown in FIGS. 9 and 10, the elastic body 3 includes a first part 3 a and a second part 3 b. The first part 3 a is disposed on the side of one direction (direction C) of the rotation of the displacement part 2. The second part 3 a is disposed on the side of the other direction (direction D) of the rotation of the displacement part 2.

As shown in FIGS. 9 and 10, in this embodiment, the plate-like member 12 is absent, and instead, plate-like members 13 and 14 are provided. The plate-like members 13 and 14 are fixed to the case part 9.

The first part 3 a of the elastic body 3 is disposed between the plate-like member 13 and the proximal portion 2 c of the displacement part 2 so as to be compressed therebetween. The second part 3 b of the elastic body 3 is disposed between the plate-like member 14 and the proximal portion 2 c of the displacement part 2 so as to be compressed therebetween.

In this embodiment, the heat flow sensor 4 is comprised of a first detection part 4 a for detecting mainly a heat flow caused by an elastic deformation of the first part 3 a of the elastic body 3, and a second detection part 4 b for detecting mainly a heat flow caused by an elastic deformation of the second part 3 b of the elastic body 3. Each of the first and second detection parts 4 a and 4 b is the same in structure as the heat flow sensor 4 described in the first embodiment. The first detection part 4 a is configured to generate a positive electromotive force when a heat flow passes from the front side to the back side of the first detection part 4 a. The second detection part 4 b is configured to generate a positive electromotive force when a heat flow passes from the front side to the back side of the second detection part 4 b.

As shown in FIGS. 9 and 10, the first detection part 4 a of the heat flow sensor 4 is disposed opposite to the elastic body 3 across the plate-like member 13. Likewise, the second detection part 4 b of the heat flow sensor 4 is disposed opposite to the elastic body 3 across the plate-like member 14. The first and second detection parts 4 a and 4 b of the heat flow sensor 4 are electrically connected to the tension calculation part 7. The first detection part 4 a generates an electromotive force in accordance with a deformation amount of the first part 3 a of the elastic body 3 when a heat flow has occurred in the first part 3 a of the elastic body 3. The second detection part 4 b generates an electromotive force in accordance with a deformation amount of the second part 3 b of the elastic body 3 when a heat flow has occurred in the second part 3 b of the elastic body 3.

The plate-like member 13 functions as an intervening part that prevents a force caused by an elastic deformation of the first part 3 a of the elastic body 3 due to the tension of the wire rod 100 from affecting the first detection part 4 a of the heat flow sensor 4. The plate-like member 14 functions as an intervening part that prevents a force caused by an elastic deformation of the second part 3 a of the elastic body 3 due to the tension of the wire rod 100 from affecting the second detection part 4 b of the heat flow sensor 4. The provision of the plate-like members 13 and 14 provides an advantage that the heat flow sensor 4 is not easily damaged.

In this embodiment, the tension calculation part 7 calculates the tension or a change of the tension of the wire rod 100 based on the electromotive force detected by the first detection part 4 a and the electromotive force detected by the second detection part 4 b of the heat flow sensor 4. More specifically, the tension calculation part 7 calculates the tension or a change of the tension of the wire rod 100 based on the difference between the electromotive force detected by the first detection part 4 a and the electromotive force detected by the second detection part 4 b of the heat flow sensor 4.

Next, the operation of the tension measuring apparatus 1 according to the fourth embodiment is explained.

As shown in FIGS. 9 and 10, the tension measuring apparatus 1 is placed at a predetermined position, and the wire rod 100 is caused to abut against the displacement part 2. At this time, the tension measuring apparatus 1 is in a state of starting measurement where the displacement part 2 of the tension measuring apparatus 1 compresses the first part 3 a and the second part 3 b to some extent while it is caused to abut against the elastic body 3.

In this embodiment, the tension measuring apparatus 1 is left in this measurement starting state for a predetermined time so that the heat generated inside the elastic body 3 due to the compression of the elastic body is sufficiently dissipated to the outside. Accordingly, in this state, the electromotive force of the heat flow sensor 4 becomes approximately zero.

In a case where the tension of the wire rod 100 increases thereafter, the displacement part 2 rotates in the direction C or D shown in FIG. 9 with the support mechanism 10 as a fulcrum as shown in FIG. 10. Here, it is assumed that the displacement part 2 rotates in the direction C. The second part 3 b of the elastic body 3 is compressed in this state than in the measurement starting state, while the first part 3 a of the elastic body 3 is released from the compression to restore from being deformed. As a result, heat occurs in the second part 3 b of the elastic body 3, while cold occurs in the first part 3 a of the elastic body 3. Accordingly, a positive electromotive force occurs in the first detection part 4 a of the heat flow sensor 4, while a negative electromotive force occurs in the second detection part 4 b of the heat flow sensor 4. The tension calculation part 7 calculates a change of the tension of the wire rod 100 based on the difference between the electromotive force that has occurred in the first detection part 4 b and the electromotive force that has occurred in the second detection part 4 b. The value of a change of the tension of the wire rod 100 calculated by the tension calculation part 7 at this time is larger than that calculated at the time of start of measurement. When heat due to compression remains in the elastic body 3 or when the elastic body 3 has heat due to circumferential heat, a positive electromotive force may occur also in the second detection part 4 b of the heat flow sensor 4.

According to this embodiment, since the tension or a change of the tension of the wire rod 100 is calculated based on the difference of the electromotive forces of the two heat flow sensors (the first and second detection parts 4 a and 4 b), an advantage that the output of the tension calculation part 7 can be increased is obtained.

In a case where the tension of the wire rod 100 decreases after the start of measurement, the displacement part 2 rotates in the direction C or D in FIG. 9 with the support mechanism 10 as a fulcrum. Here, it is assumed that the displacement part 2 rotates in the direction D. In this case, the second part 3 b of the elastic body 3 is released from the compression to restore from being deformed. Therefore, since cold occurs inside the second part 3 b of the elastic body 3, the electromotive force occurring in the second detection part 4 b of the heat flow sensor 4 decreases. On the other hand, since the first part 3 a of the elastic body 3 is compressed, heat occurs inside the first part 3 a of the elastic body 3. As a result, the difference in electromotive force between the first detection part 4 a and the second detection part 4 b decreases, typically to a negative value. Accordingly, it is detected as a decrease of the tension of a belt 100 by an abnormality estimation part 7.

According to the tension measuring apparatus 1 according to this embodiment, both the tension and a change of the tension can be measured.

According to the tension measuring apparatus 1 according to this embodiment, since the plate-like member 14 is provided, the heat flow sensor 4 is not easily damaged, like the second embodiment.

The tension measuring apparatus 1 according to this embodiment provides the advantage that the relationship between the tension of the wire rod 100 and the displacement of the elastic body 3 or the relationship between the tension of the wire rod 100 and the electromotive force of the heat flow sensor 4 can be set in a wide range like the second embodiment.

According to the tension measuring apparatus 1 according to this embodiment, since the tension or a change of the tension of the wire rod 100 is calculated based on the difference between the electromotive forces of the two heat flow sensors (the first and second detection parts 4 a and 4 b), the output of the tension calculation part 7 can be increased. The output of the tension calculation part 7 in this embodiment is approximately twice as that in the case of using a single heat flow sensor.

Further, according to this embodiment, since the tension or a change of the tension is calculated based on the difference between two electromotive forces of the two heat sensors (the first and second detection parts 4 a and 4 b), and accordingly, temperature drifts included in the two electromotive forces cancel each other, it is possible to prevent the temperature drifts from affecting the output of the tension calculation part 7. That is, in the case where only the single heat flow sensor 4 is provided, it is not possible to determine, when the electromotive force of the heat flow sensor 4 has increased, whether it is due to an increase of the tension of the wire rod 100 causing the elastic body 3 to be deformed, or it is due to an increase of the circumferential temperature. On the other hand, in the case where two heat flow sensors (the first and second detection parts 4 a and 4 b) are provided, since the tension or a change of the tension of the wire rod 100 is calculated based on the difference between the two electromotive forces of the two heat flow sensors, it is possible to determine that the elastic body 3 has been deformed due to an increase of the tension of the wire rod 100 removing the effect of a change of the circumferential temperature. Specifically, in this embodiment, the heat flow sensor 4 is configured to generate a positive electromotive force when a heat flow passes from the front side to the back side thereof, and the tension or a change of the tension of the wire rod 100 is calculated based on the difference in electromotive force between the first and second detection parts 4 a and 4 b as two heat flow sensors. Accordingly, it is possible to remove the temperature drift caused by a heat flow passing from the back side to the front side of each of the first detection part 4 a and the second detection part 4 b, and remove the temperature drift caused by a heat flow passing from the front side to the back side of each of the first detection part 4 a and the second detection part 4 b. Incidentally, the effect of the temperature drift caused by a heat flow passing from the back side to the front side of the first detection part 4 a and a heat flow passing from the back side to the front side of the second detection part 4 b can be removed by calculating the tension or a change of the tension of the wire rod 100 based on the sum of the electromotive forces of the two heat flow sensors (the first and second detection parts 4 a and 4 b), or by causing the second detection part 4 b to generate a positive electromotive force when a heat flow passes from the front side to the back side of the second detection part 4 b.

Other Embodiments

It is a matter of course that various modifications can be made to the above described embodiments as described below.

In the first to fourth embodiments, the displacement part 2 includes the roller portion 2 b or 2 d to feed the wire rod 100. However, the roller portion 2 b or 2 d may not be provided if the wire rod 100 is fed by causing the wire rod 100 to abut against the displacement part 2. That is, as shown in FIGS. 11 and 12, the wire rod 100 may be fed by causing the wire rod 100 to abut against a surface 2 e of the displacement part 2. In this case, it is preferable that the coefficient of friction of the surface 2 e is small so that the wire rod 100 abutting against the surface 2 e can easily slide thereon. The tension calculation part 7 and the display part 8 are omitted from illustration in FIGS. 11 and 12. The arrow Y15 in FIG. 11 shows the direction of displacement of the elastic body 3 at a time when the tension of the wire rod 100 has increased.

The above explained preferred embodiments are exemplary of the invention of the present application which is described solely by the claims appended below. It should be understood that modifications of the preferred embodiments may be made as would occur to one of skill in the art. 

What is claimed is:
 1. A tension measuring apparatus comprising: a displacement part that is displaced in accordance with tension or a change of the tension of a wire rod when the displacement part is caused to abut against the wire rod to receive the tension of the wire rod; an elastic body that is elastically deformed in accordance with displacement of the displacement part; a heat flow sensor that detects a heat flow caused by elastic deformation of the elastic body; and a heat conducting member disposed adjacently to the heat flow sensor, wherein the heat flow sensor is disposed between the elastic body and the heat conducting member.
 2. The tension measuring apparatus according to claim 1, further comprising a case part for supporting the elastic body and a support mechanism that causes the case part to rotatably support the displacement part, wherein the displacement part rotates with the support mechanism as a fulcrum, and the elastic body is elastically deformed in accordance with the displacement of the displacement part due to rotation of the displacement part.
 3. The tension measuring apparatus according to claim 2, further comprising a tension calculation part that calculates the tension of the wire rod based on the heat flow detected by the heat flow sensor, wherein the elastic body includes a first part and a second part, the displacement part compresses the second part and restores the first part when the displacement part rotates in a first rotational direction, and restores the second part and compresses the first part when the displacement part rotates in a second rotational opposite to the first rotational direction, the heat flow sensor includes a first detection part for detecting a heat flow caused by elastic deformation of the first part to generate an electromotive force corresponding thereto and a second detection part for detecting a heat flow caused by elastic deformation of the second part to generate an electromotive force corresponding thereto, and the tension calculation part calculates the tension of the wire rod based on an electromotive force generated by the first detection part and an electromotive force generated by the second detection part.
 4. The tension measuring apparatus according to claim 2, wherein the displacement part rotates when caused to abut against the wire rod to feed the wire rod.
 5. The tension measuring apparatus according to claim 1, further comprising an intervening part that intervenes between the displacement part and the heat flow sensor to prevent a force caused by the elastic deformation of the elastic body from affecting the heat flow sensor. 